Many fishes, amphibians and reptiles possess a pineal complex at least part of which is specialized for photoreception. These photosensitive organs contain receptor cells which are structurally similar to vertebrate cones, but the remainder of their neural organization is much simpler than that of the vertebrate retina. In spite of this anatomical simplicity, some of these pineal complexes are capable of producing color opponent responses with unusual properties, and some of them also display unusual adaptational characteristics. The pineal complexes are amenable to experimental manipulation, sometimes without removing the pineal from the animal. Using a combination of electrophysiology and electron microscopy, we will study the neural circuitry of these organs in an attempt to elucidate the physiology of photoreceptor synapses, and of photoreceptor light and dark adaptation, in the vertebrate retina.